H.—34.

Economic Geology. The silica sands in the Mangatarata beds have been used in foundry work. The pumiceous silts of these beds could be used in sandsoaps or as a filler in bituminous surfaces. The shelly limestones of the Te Aute and Petane could be used for agricultural purposes, but are not of high grade. The gravels of Pleistocene and Recent age are much quarried for road-making material. Faint oil indications are known only in the region adjoining the Whangai Range. The overlap of: Opoiti beds on the greywackes in the Waewaepa Range makes the chances of finding oil-bearing bed in the Dannevirke basin highly problematical. Motuotaraia North-eastebn-and Pourerere Survey Districts. Structure. East of the Tangatupara Ranges there is a broad synclinal depression of Ihungia mudstones representing the northern continuation, of the Akitio Syncline. Between the Whangai argillites of the ranges and the Ihungia mudstones the Wanstead formation is usually present, but longitudinal faulting has obscured the stratigraphical relations. Some three miles east of the ranges the syncline is interrupted by an anticline which runs north-north-east. across Pourerere north-west. This anticline discloses Bortonian bentonite and greensands south of the Kerrytown Road - Farm Road junction, but farther north the special facies of the Lower Ihungia, in the form of yellow calcareous mudstones, appears. The anticline crosses the Pourerere Road where it cuts a low ridge formed of Wanstead and Whangai formations. East of the anticline the Ihungia mudstones reappear dipping gently west or flat-lying. They are capped by Tutamoe sandstones, which form the prominent summits around Omakere Station—namely, Omakere Hill, Trig. C, Trig. A, and Trig. X. The region between these summits and the coast is very complicated and requires a closer study in the light of micro-faunal evidence. There is an axial rise towards the north and perhaps several cross-faults with an approximate east-west orientation bringing older beds to the surface in the north. One and a half miles west of Clareinch Station the Ihungia mudstones assume a westerly dip, and Cretaceous beds appear to the east, forming a complex anticline. These Cretaceous beds are clearly visible in the upper part of the Mangakuri Stream, but both their structure and stratigraphy is obscure. The rocks are generally faulted and sheared, and slumping hides many of the critical contacts. There appear to be formations exactly resemblimg the Whangai, the Tapuwaeroa, and the Raukumara, as well as bentonite in this anticline. The Cretaceous beds are overlain by the yellow calcareous mudstone facies of the Lower Ihungia. Along the Mangakuri Road a fault-zone separates the anticline from a thin strip of Ihungia mudstones, but another anticline of Cretaceous mudstones and bentonite again occupies all the country to the east between the road and the coast. The Cretaceous beds can be traced as far as Pourerere, where mudstones, presumably of Ihungia age, are faulted against the eastern margin of the Cretaceous. The country to the south and south-east of Clareinch Station is occupied by Ihungia mudstones. The presence of gas-springs and earthquake traces at Roundaway Station on the Pourerere Road marks the continuation of the Pourerere fault-zone noted on Mangakuri Road. Thence the Pourerere Fault must extend along the western edge of Frenchman's Cap, where it has a downthrow to the east. A transverse east-west fault with a downthrow to the south probably runs towards the coast from the north of Frenchman's Cap. This outstanding hill is formed of hard, shelly conglomerates and calcareous sandstones of Tutamoe age, which have a steep easterly dip. Succeeding these beds to the east of the summit are softer sandstones and mudstones of Tutamoe age and Mapiri mudstones, which are difficult to distinguish lithologically from the Ihungia. A marked anticline of Tutamoe sandstones reappears about two miles east of Frenchman's Cap. Stratigraphy. Raukumara Series.—ln a stream some 110 chains north-north-west of Clareinch Station massive dark blue-grey mudstones have yielded abundant Inoceramus. These are similar to the Inoceramus found in the Whangai Range, and Dr. Finlay reports a microfauna similar to that of the Mangaotane mudstone. Tafuwaeroa Series. —The lowest part of the beds, here classed as Tapuwaeroa, are well exposed in Mangakuri Stream, 105 chains west of Clareinch Homestead. They consist of greenish white argillite that weathers to a rusty colour, and bands of jade-green sandstone, all intricately folded and sheared. These beds are. overlain by carbonaceous sandstone and mudstone with occasional bands of breccia made up of fragments of white argillite. At another locality similar beds pass up into a fine-grained conglomerate containing Ostrea lapillicola. Cannon-ball sandstone also occurs. The group, as a whole, is characterized by bands of carbonaceous mudstone and current-bedded grey sandstone and particularly by fine-grained conglomerate of greywacke and metamorphic rocks containing Ostrea lapillicola and many fragments of Inoceramus. Wanstead Series.—This consists of fine grey mudstones and bentonitic clays. Ihungia Series. —The special calcareous facies of the lower Ihungia is often present. The higher parts of the Ihungia consist of fine dark grey mudstones.

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